The present invention relates generally to the field of Internet telephony, and more particularly to a method of and system for providing address definition for public switched network terminated calls that use Internet telephony services.
The existing public switched telephone network (PSTN) environment provides a rich set of telephony services. In order to work properly, the services depend on address information that is carried as part of the call setup process. This address information includes the called party number and two qualifiers to the called party number. These qualifiers are the nature of address (NOA) and the numbering plan indicator (NPI).
The called party number and the qualifiers are used in the PSTN to determine how to handle calls. The nature of address can be subscriber, national, or international. The numbering plan indicator can be public (E. 164) or private. A dialed number address with NOA and NPI values indicating the called party number is an international public number will be routed differently than the same number that has NOA and NPI values indicating that it is in a private numbering plan.
Efforts are currently underway to extend the services to devices connected to Internet protocol (IP) networks. One protocol that has been developed to handle the called related signaling in the IP based networks is the session initiation protocol (SIP). The addressing mechanism built into the SIP specification supports only global and local numbers. The SIP specification does not support the NOA and NPI qualifiers used in the PSTN. As a result, is not possible to support all of the existing PSTN services when one leg of a call must pass through an IP network or terminate to the device on an IP network.
The present invention provides a method of and system for providing IP telephony services by mapping a telephony signaling protocol called party number nature of address indicator to an Internet signaling protocol nature of address indicator and mapping a telephony signaling protocol called party number numbering plan indicator to an Internet signaling protocol numbering plan indicator. The present invention is preferably implemented by extending the session initiation protocol (SIP) invite request called party URL to include a nature of address parameter and a numbering plan parameter. The system of the present invention provides a gateway that performs the mapping.